PDE4B and hydrops fetalis: However, PDE4B overexpression had no effect on cell surface area and intracellular ROS level but partially inhibited the increase in cell surface area and intracellular ROS level induced by ISO stimulation (Fig. 2G and H), which is consistent with a previous report that cardiac PDE4B is beneficial to counteract the detrimental effect of excessive sympathetic system activation in HF [11].